Where New Species Come From
Here's a challenge: Physicist writing about evolution! But it is a topic dear to my heart for its simplicity and yet is a blueprint for the entire living history of the earth. It's simple in the same way Newton's three laws are simple and yet cover the motion of ANYTHING including the planets.
Evolution is too big for me to cover appropriately in one blog entry and I won't try. I am ‘currently reading’ Darwin’s Origin of Species and the quotes are because I read it and then go on to other things and then read some more. Suffice it to say that it is a surprisingly coherent read for the non-biologist. It showcases the extreme detail of work and thought that Darwin used to build his theory.
Darwin uses many examples from the wild and from simple, well worn (if not fully understood) farming techniques. The string of logic that really hit me goes like this.
1. A farmer can select for, say, sheep with thick fur. He does this by only allowing certain sheep to make baby sheep. That's his 'selection process'. Before we knew about DNA and the machinery of genetics, farmers knew that traits tended to be passed on from parents to offspring. You use this to make fast racehorses, pretty roses, and, yes, puffy sheep. Key word here is ‘select’.
2. Darwin noted that offspring are mostly like the parents with slight variations - or mutations even.
3. Nature will ‘naturally select’ for traits that make it more likely to survive* in the wild and produce more offspring.
4. So, you have variety/mutation in any species and you have a natural selection process going on and that’s how species evolve over the course of millions and millions of generations.
Evolution in the laboratory.
In an interesting experiment, Richard Lenski of Michigan State started 12 separate groups of Escherichia coli bacterium all descendants from a single bacterium and let them go through about 44,000 generations over 20 years.
All 12 groups showed similar changes such as bigger cells. But somewhere around the 31,000 generation one group acquired the ability to metabolize citrate that they normally cannot use. By keeping frozen groups every 500 generations he was able to go back and ‘replay’ the evolution to show that indeed some random mutation in this one group sometime after the 20,000 generation.
In short they're watching evolution work right in the laboratory. Notice the measure of time here. 44,000 generation in 20 years. How long would 44,000 generations take for a species that lives say 20 years? 44,000 x 20 = 880,000 years. It’s the slow tromp of evolution that tends to cloud our understanding of it. Reminds me of Haley figuring out that many of the comet sightings over the course of history were the same comet which must be orbiting the sun! Things that take place on a time scale well beyond our lifetimes are hard to trick out of the data.
*Darwin himself never used the phrase ‘survival of the fittest’
Reading
I recommend reading Your Inner Fish by Neil Shubin
Or watching the PBS series of the same name
Also give Origin and chance.
Anything by Jerry Coyne including “Why Evolution is True”
Links
Myths and Misconceptions
Arguments back and forth
Evolution is too big for me to cover appropriately in one blog entry and I won't try. I am ‘currently reading’ Darwin’s Origin of Species and the quotes are because I read it and then go on to other things and then read some more. Suffice it to say that it is a surprisingly coherent read for the non-biologist. It showcases the extreme detail of work and thought that Darwin used to build his theory.
Darwin uses many examples from the wild and from simple, well worn (if not fully understood) farming techniques. The string of logic that really hit me goes like this.
1. A farmer can select for, say, sheep with thick fur. He does this by only allowing certain sheep to make baby sheep. That's his 'selection process'. Before we knew about DNA and the machinery of genetics, farmers knew that traits tended to be passed on from parents to offspring. You use this to make fast racehorses, pretty roses, and, yes, puffy sheep. Key word here is ‘select’.
2. Darwin noted that offspring are mostly like the parents with slight variations - or mutations even.
3. Nature will ‘naturally select’ for traits that make it more likely to survive* in the wild and produce more offspring.
4. So, you have variety/mutation in any species and you have a natural selection process going on and that’s how species evolve over the course of millions and millions of generations.
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| Penn State |
Evolution in the laboratory.
In an interesting experiment, Richard Lenski of Michigan State started 12 separate groups of Escherichia coli bacterium all descendants from a single bacterium and let them go through about 44,000 generations over 20 years.
All 12 groups showed similar changes such as bigger cells. But somewhere around the 31,000 generation one group acquired the ability to metabolize citrate that they normally cannot use. By keeping frozen groups every 500 generations he was able to go back and ‘replay’ the evolution to show that indeed some random mutation in this one group sometime after the 20,000 generation.
In short they're watching evolution work right in the laboratory. Notice the measure of time here. 44,000 generation in 20 years. How long would 44,000 generations take for a species that lives say 20 years? 44,000 x 20 = 880,000 years. It’s the slow tromp of evolution that tends to cloud our understanding of it. Reminds me of Haley figuring out that many of the comet sightings over the course of history were the same comet which must be orbiting the sun! Things that take place on a time scale well beyond our lifetimes are hard to trick out of the data.
*Darwin himself never used the phrase ‘survival of the fittest’
Reading
I recommend reading Your Inner Fish by Neil Shubin
Or watching the PBS series of the same name
Also give Origin and chance.
Anything by Jerry Coyne including “Why Evolution is True”
Links
Myths and Misconceptions
Arguments back and forth
Comments
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